Bovine cytotoxic T cell clones which recognize lymphoblasts infected with two antigenically different stocks of the protozoan parasiteTheileria parva

摘要

AbstractThe Muguga and Marikebuni stocks ofTheileria parvadiffer on the basis of cross‐protection and in their schizont antigen profile determined with a panel of parasitespecific monoclonal antibodies. The phenotype and specificity of six cytotoxic T cell clones generated from an animal immunized againstT. parva(Marikebuni) were investigated. All six clones had the BoT2+BoT4−BoT8+phenotype, were dependent on both specific antigen and T cell growth factor for proliferation and were restricted by determinants on class I major histocompatibility complex molecules. The clones killed target cells infected with either the Muguga or Marikebuni stocks of the parasite; the target cell lines tested included T cell clones which were infectedin vitrowith the two parasite stocks and subsequently recloned. The specificity of these cytotoxic T cell clones contrasts with that of T cell clones generated previously from animals immunized againstT. parva(Muguga), in that the latter were specific for target cells infected with the Muguga stock of the parasite. Moreover, one of the clones generated againstT. parva(Marikebuni) was restricted by the same major histocompatibility complex molecule as the Muguga‐specific T cell clones. The difference in parasite strain‐specificity between the two sets of clones appears to reflect the capacities of the two parasite stocks to cross‐protect, since animals immunized againstT. parva(Marikebuni) are protected against challenge withT. parva(Muguga) whereas a proportion of animals immunized withT. parva(Muguga) are susceptible to challenge withT. parva(Marikebuni). Another difference between the two sets of T cell clones was that those generated againstT. parva(Marikebuni) only killed a proportion of cells of a given cell line in a 4‐h cytotoxicity assay, whereas Muguga‐specific T cells invariably kill the majority of cells. However, despite this partial killing, the clones markedly inhibited growth of parasitized cell lines when cultured with them for a per